Department of Conservative Dentistry, School of Dentistry, Dental Research Institute, Pusan National University, Yangsan, Korea.
Department of Conservative Dentistry, School of Dentistry, Kyungpook National University, Daegu, Korea.
J Endod. 2017 Nov;43(11):1872-1877. doi: 10.1016/j.joen.2017.05.025. Epub 2017 Sep 23.
The purpose of this study was to compare the bending stiffness, cyclic fatigue, and torsional fracture resistances of heat-treated and conventional nickel-titanium rotary instruments.
V-Taper 2 (VT2; #25/.08), V-Taper 2H (V2H; #25/.06), Hyflex CM (HCM; #25/.06), HyFlex EDM (HDM; #25/variable taper), and ProTaper Next X2 (PTN; #25/variable taper) were tested. The bending stiffness was measured with the customized device (AEndoS), and the files (n = 15) were fixed at 3 mm from the tip and bent at 45° with respect to their long axis. Cyclic fatigue resistance was tested by pecking and rotating instruments (n = 15) in artificial canal with a 7.8-mm radius and 35° angle of curvature until fracture. The ultimate torsional strength and toughness were estimated by using AEndoS. The file tip of 5 mm was fixed between resin blocks and driven clockwise at 20 rpm until fracture. The results were analyzed by using one-way analysis of variance and Duncan post hoc comparison. The fracture surfaces and longitudinal aspect of each group were examined under the scanning electron microscope.
CM-wire instruments had lower bending stiffness than others. HDM showed the highest cyclic fatigue resistance, followed by VTH and HCM (P < .05). VT2 showed the highest ultimate strength, followed by HDM, VTH-PTN, and HCM. HDM and VT2 showed significantly higher toughness than VTH, HCM, and PTN (P < .05). Scanning electron microscope analysis showed typical fractographic features of cyclic fatigue and torsional fractures.
CM-wire instruments showed higher flexibility and cyclic fatigue resistance than M-wire and conventional nickel-titanium instruments. Large cross-sectional area and conventional nickel-titanium showed high torsional resistance.
本研究旨在比较热处理镍钛旋转器械和传统镍钛旋转器械的弯曲刚度、循环疲劳和抗扭强度。
对 V-Taper 2（VT2；#25/.08）、V-Taper 2H（V2H；#25/.06）、Hyflex CM（HCM；#25/.06）、HyFlex EDM（HDM；#25/变锥度）和 ProTaper Next X2（PTN；#25/变锥度）进行了测试。使用定制设备（AEndoS）测量弯曲刚度，将器械（n=15）固定在距尖端 3mm 处，使其长轴与弯曲轴成 45°角弯曲。通过在半径为 7.8mm、曲率角为 35°的人工根管中进行敲击和旋转器械（n=15）来测试循环疲劳阻力，直到器械断裂。使用 AEndoS 估计器械的最大抗扭强度和韧性。将 5mm 的器械尖端固定在树脂块之间，以 20rpm 的速度顺时针驱动，直到器械断裂。使用单向方差分析和 Duncan 事后比较对结果进行分析。用扫描电子显微镜观察每组的断裂面和纵向情况。
CM 丝器械的弯曲刚度低于其他器械。HDM 的循环疲劳阻力最高，其次是 VTH 和 HCM（P<.05）。VT2 的最大强度最高，其次是 HDM、VTH-PTN 和 HCM。HDM 和 VT2 的韧性明显高于 VTH、HCM 和 PTN（P<.05）。扫描电子显微镜分析显示出循环疲劳和扭断的典型断口特征。
CM 丝器械比 M 丝和传统镍钛器械具有更高的柔韧性和循环疲劳阻力。大横截面积和传统镍钛具有较高的抗扭强度。
